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RE: Say this slowly: theropoda is paraphylitic, theropoda is paraphlyitic.....



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> ELurio@aol.com
>
>     They also look extremely like other theropods.  Your idea has
> to explain
>
> why coelurosaurs and birds have so many detailed similarities with
>
> theropods, especially since they have zero similarity to
> Longisquama.  What
>
> reason is there NOT to think that coelurosaurs and other thropods aren't
>
> related?  Why do we need this particular elaborate story? >>
>
> Because it fits the fossil record? The ground up hypothisis is even more
> ridiculous sounding, and is only popular because the aboreal
> protobird had
> never been found.
>

Eric,

You are guilty (as a lot of people are, it has to be admitted) of conflating
two independant ideas:
I) the hypothesis of the origin of the taxon Aves (i.e., what is the sister
group of the birds);
II) the hypothesis of the origin of avian flight (i.e., in what environment
did the bird lineage obtain flight).

These are actually two separate ideas.  There are "ground-up coelurosaur"
folks (Padian, Ostrom, etc.), "trees-down coelurosaur" folks (Chatterjee,
Currie to a certain degree), and "trees-down anything-but-dinosaurs" folks
(the Feducciaries).  Although I don't know of any "ground-up
anything-but-dinosaurs" proposals, but there is nothing logically wrong with
that possibility.

Incidentally, many workers (old-timers like Ostrom, for example) consider
Theropoda to be paraphyletic, in so far as they retain the traditional
grouping and do not include birds within Theropoda.  However, these same
individuals recognize that birds are dinosaur descendants.

As for your idea that Theropoda is polyphyletic: it is to laugh, not to put
too fine a point on it.  Polyphyly of Primates or of Cetacea seems more
likely than a polyphyletic Theropoda: the theropods were very much
variations on the same detailed anatomical design.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-314-7843